以下检查中，哪项是心脏瓣膜病的首选检查方法（）
A.MRI
B.D-US
C.CT
D.X-ray
E.冠脉造影
参考答案：B
— I'd like Johnson to take the job.
— He is _______. Better not add to his workload.
A．out of place
B．oul of order
C．out of shape
D．out of question
凸轮轴的动力由（）而来。
A、启动电机
B、曲轴
C、液力
D、电力
